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Terminology, investigation procedures and deciding whether to investigate

Deciding whether to investigate

This section provides information on the decision process for investigating a transport safety matter.


The ATSB is resourced each year to undertake a finite number of investigations. It is acknowledged, however, that an occurrence with a large number of passenger fatalities would represent a major accident that may require supplementary funding.

Following the initial assessment of a notification, a decision is made whether or not to conduct an investigation. Some  occurrences may be subject to a limited scope Short fact gathering investigation. These short investigations are published periodically in Short Investigation Bulletins, which include about 10 individual reports each issue. Refer to the investigation levels in Classifying.

Priorities for investigating

The ATSB's primary focus is on enhancing safety with respect to fare paying passengers, and in particular, those transport safety matters that may present a significant threat to public safety and are the subject of widespread public interest. The ATSB therefore needs to direct significant attention to identifying systemic failures in aviation, marine and rail mass public transport systems, that have the potential to result in catastrophic accidents and which are often characterised by large numbers of fatalities and serious injuries.

In addition, the ATSB has observed that many accidents involve repetition of past occurrences where the contributing factors are similar and the safety issues are well known. In these circumstances, the likely safety benefits and lessons may not always justify allocating significant resources. In those cases, the ATSB may undertake a limited fact-gathering investigation only; if so, it will outline the reasons an extensive investigation has not been conducted. Equally, there is often as much or more to be learned from serious incidents or patterns of incident as there is from accidents and where appropriate, the ATSB will give priority to these sorts of investigation.

The following broad hierarchies for aviation, marine and rail which reflect the priorities described above, must be taken into account when deciding whether to investigate and when determining the level of investigation response.

Aviation broad hierarchy

In applying these guidelines, the ATSB will allocate its resources in line with the following broad hierarchy of operation types:

1. Passenger transport - large aircraft.
2. Passenger transport - small aircraft:
- RPT and charter on small aircraft
- humanitarian aerial work (for example, RFDS, SAR flights).
3. Commercial (that is, fare paying) recreation (for example, joy flights).
4. Aerial work with participating passengers (for example, news reporters, geological surveys).
5. Flying training.
6. Other aerial work:
- non-passenger carrying aerial work (for example, agriculture, cargo)
- private transport/personal business.
7. High risk personal recreation/sports aviation/experimental aircraft operations.

Marine broad hierarchy

In applying these guidelines, the ATSB will allocate its resources in line with the following broad hierarchy of marine operation types:

1. Passenger operations.
2. Freight and other commercial operations.
3. Non-commercial operations.

Rail broad hierarchy

In applying these guidelines, the ATSB will allocate its resources in line with the following broad hierarchy of rail operation types:

1. Mainline operations that impact on passenger services.
2. Freight and other commercial operations.
3. Non-commercial operations.

Level of response

The level of investigation response is determined by resource availability and such factors as detailed below. These factors are presented in no particular order and may, depending on the circumstances, vary in the degree to which they influence the ATSB's decision to investigate and the level of response.

• anticipated safety value of an investigation, including the likelihood of furthering the understanding of the scope and impact of any safety system failures
• likelihood of safety action arising from the investigation, particularly of national or global significance
• existence and extent of fatalities/serious injuries and/or structural damage to transport vehicles/other infrastructure
• obligations or recommendations under international conventions and/or codes
• nature and extent of public, interest, in particular the potential impact on public confidence in the safety of the transport system
• existence of supporting evidence or requirements to conduct a special investigation based on trends
• relevance to an identified and targeted safety program
• the extent of resources available and projected to be available in the event of conflicting priorities
• the risks associated with not investigating including consideration of whether, in the absence of an ATSB investigation, a credible safety investigation by another party is likely
• timeliness of notification
• training benefit for ATSB investigators.

Initiation of an investigation

With increasing resource pressure, initiation of a full investigation can only be done by the relevant manager in consultation with the relevant General manager and the Chief Commissioner.

Short investigations can be initiated by the relevant General Manager.

Fatal accidents not investigated

The ATSB's justification for electing not to investigate a notifiable fatal accident will be documented in the database record for that occurrence.

Trend monitoring

Occurrences that may fit the definition of an aviation safety accident or incident but that in isolation do not represent a risk to safe aviation, do not require individual investigation.

Such occurrences may be referenced during trend monitoring of occurrences with similar factors. All occurrences are entered into the ATSB’s data base for such purposes.

Marine and rail do not have the same weight in numbers for trend monitoring, although the managers monitor obvious trends in accidents in the industry which forms a part of the decision making process to decide whether or not to investigate.



This section provides information on the classification process.


The objective of the classification process is to quickly identify and manage appropriately, including the allocation of resources, those occurrences that:

• require detailed investigation
• need to be recorded by the ATSB for future research and statistical analysis
• need to be passed to other agencies for further action
• do not contribute to transport safety.

Three ways to action

Transport safety matter reports can be actioned in one of three ways to contribute to the Bureau's functions.

1. A report of an occurrence that suggests that a safety issue may exist should be investigated immediately. Investigation may lead to the identification of the safety issue, including its significance, and provide the justification for safety action.

2. A report of an occurrence that may not warrant a full investigation but which would benefit from additional fact gathering for future safety analysis to identify safety issues or safety trends.

3. Basic details of an occurrence, based primarily on the details provided in the initial occurrence notification, can be recorded in the database to be used in future safety analysis to identify safety issues or safety trends.

Note: In the third approach, the occurrence is not investigated immediately, but may be the subject of a future investigation.

Pros/cons first approach

The advantages of the first approach are a quick identification of a safety issue, and a thorough investigation of all the data relating to the occurrence.
The disadvantage in this approach is that a full investigation uses considerable resources and time.

Pros and cons of the second approach

The advantage of the second approach is that a richer data set for a greater number of occurrences is generated with minimal resource overhead which, in turn, is likely to result in improved future research and statistical analysis outcomes. These short, fact gathering investigations also provide an opportunity to upgrade to a full investigation when the initial fact gathering suggests that the issues are more complex and warrant more detailed examination and analysis.

Pros/cons third approach

The advantage of the third approach is that it can be used for a large number of occurrences using far fewer resources than the first two approaches.

The major disadvantage is that a safety issue may not be identified until after a considerable period of time.

Who classifies?

Classifying a transport safety matter is normally the task of the Notifications Officer; however, the Manger Notifications and Confidential Reporting needs to liaise with the relevant Manager or General Manager who make any decision regarding investigation, in consultation with the Chief Commissioner where necessary.


ATSB controlled accident sites

The Australian Transport Safety Bureau is responsible for ensuring the occupational health and safety of personnel entering accident sites which it controls. Recent on-site accident investigations have brought to our attention that some personnel wishing to enter accident sites are not appropriately or adequately equipped to be on the site.

In order for the ATSB to meet its primary duty of care as far as reasonably practicable under section 19 of the Work Health and Safety Act 2011 you are informed that should your personnel wish to enter an ATSB controlled accident site they must be appropriately equipped and have a record of inoculations.

Dependent on the hazardous nature of the site, personnel may also be required to provide evidence of having completed of a Bio-Hazard Awareness course, which is accepted by the USA Federal Aviation Administration or the ATSB equivalent qualification, before being permitted to handle anything on the site. The ATSB recognises that some aviation professionals may have legitimate reasons for wishing to enter accident sites. The ATSB will, as far as possible, accommodate such requests, but has the ultimate decision over accident sites under its control.

The following minimum current vaccination record is required:

  • Hepatitis B
  • Tetanus toxoid

The following minimum Personal Protective Equipment is required:

  • Boots steel toed
  • Overalls including disposable overalls
  • Boot covers or gumboots (preferably steel toed)
  • Latex/Nitrile/Rubber Gloves
  • Leather riggers gloves
  • Safety Glasses/Goggles/Face Shield
  • Hearing Protection (Ear plugs)
  • Hard hat
  • Breathing protection apparatus
    • Breathing apparatus needed may range from paper nose and mouth guard, to a respiratory mask meeting the Australian Standard AS/NZS 1715:2009  Selection, use and maintenance of respiratory protective equipment.

Some sites may be contaminated by bio-hazards. Accordingly, in such cases the investigator in charge has a duty of care to require evidence of successful completion of a Blood Borne Pathogens bio-hazard course approved by either the US Federal Aviation Administration or an ATSB equivalent qualification before allowing anyone onto an ATSB controlled site.

These requirements are necessary to ensure that the ATSB meets its statutory obligations under section 19 of the Work Health and Safety Act 2011.

Section 19 states:

Primary duty of care

1) A person conducting a business or undertaking must ensure, so far as is reasonably practicable, the health and safety of:

a) workers engaged, or caused to be engaged by the person; and

b) workers whose activities in carrying out work are influenced or directed by the person;

while the workers are at work in the business or undertaking.

2) A person conducting a business or undertaking must ensure, so far as is reasonably practicable, that the health and safety of other persons is not put at risk from work carried out as part of the conduct of the business or undertaking.

3) Without limiting subsections (1) and (2), a person conducting a business or undertaking must ensure, so far as is reasonably practicable:

a) the provision and maintenance of a work environment without risks to health and safety; and

b) the provision and maintenance of safe plant and structures; and

c) the provision and maintenance of safe systems of work; and

d) the safe use, handling and storage of plant, structures and substances; and

e) the provision of adequate facilities for the welfare at work of workers in carrying out work for the business or undertaking, including ensuring access to those facilities; and

f) the provision of any information, training, instruction or supervision that is necessary to protect all persons from risks to their health and safety arising from work carried out as part of the conduct of the business or undertaking; and

g) that the health of workers and the conditions at the workplace are monitored for the purpose of preventing illness or injury of workers arising from the conduct of the business or undertaking.


Purpose of safety investigations

The ATSB is responsible for investigating accidents and other transport safety matters involving civil aviation, marine and rail operations in Australia that fall within Commonwealth jurisdiction, as well as participating in overseas investigations involving Australian registered aircraft and ships. A primary concern is the safety of commercial transport, with particular regard to fare-paying passenger operations. The ATSB performs its functions in accordance with the provisions of the Transport Safety Investigation Act 2003 and Regulations and, where applicable, relevant international agreements.

The object of a safety investigation is to identify and reduce safety-related risk. ATSB investigations determine and communicate the safety factors related to the transport safety matter being investigated. The terms the ATSB uses to refer to key safety and risk concepts are set out in the section: Terminology Used in this Report.

It is not a function of the ATSB to apportion blame or determine liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner.


Developing safety action

Central to the ATSB's investigation of transport safety matters is the early identification of safety issues in the transport environment. The ATSB prefers to encourage the relevant organisation(s) to initiate proactive safety action that addresses safety issues. Nevertheless, the ATSB may use its power to make a formal safety recommendation either during or at the end of an investigation, depending on the level of risk associated with a safety issue and the extent of corrective action undertaken by the relevant organisation.

When safety recommendations are issued, they focus on clearly describing the safety issue of concern, rather than providing instructions or opinions on a preferred method of corrective action. As with equivalent overseas organisations, the ATSB has no power to enforce the implementation of its recommendations. It is a matter for the body to which an ATSB recommendation is directed to assess the costs and benefits of any particular means of addressing a safety issue.

When the ATSB issues a safety recommendation to a person, organisation or agency, they must provide a written response within 90 days. That response must indicate whether they accept the recommendation, any reasons for not accepting part or all of the recommendation, and details of any proposed safety action to give effect to the recommendation.

The ATSB can also issue safety advisory notices suggesting that an organisation or an industry sector consider a safety issue and take action where it believes it appropriate. There is no requirement for a formal response to an advisory notice, although the ATSB will publish any response it receives.


How ATSB safety investigation reports are organised

ATSB investigation reports are organised with regard to international standards or instruments, as applicable, and with ATSB procedures and guidelines. Reports normally contain the following main parts:

Safety summary

Provides an upfront, one-page summary of ‘What happened’, ‘What the ATSB found’, ‘What’s been done as a result’, and any broader 'Safety message'.  

The occurrence

The Occurrence provides a description of the occurrence sequence of events and, if relevant, the consequences of the occurrence in terms of injuries and damage. It is an expanded version of the ‘What happened’ section of the Safety summary.


The Context provides additional information necessary to help the reader understand the Safety analysis, and to some extent The occurrence. The information is intended to be relevant to the occurrence, rather than included just because it was collected. Safety analysis The Safety analysis provides a detailed discussion of the safety factors identified during the investigation. It provides the evidence and argument required to support the Contributing factors and Other factors that increase risk, and it is an expanded version of the ‘What the ATSB found’ section of the Safety summary. It should also outline the basis for the ‘Safety message’ section of the Safety summary.


Based on the analysis of the safety factors identified during the investigation, the Findings presents three categories of findings: Contributing factors, Other factors that increase risk, and Other findings. 

Safety issues and actions

This section summarises all the ‘safety issues’, or system problems that were identified during the investigation and details what safety action has been taken, or is planned to be taken by relevant parties to address those issues.


Contains additional information that supports the report, for example, specialist reports on materials failure or flight data analysis.

Note: Not all parts described above will be applicable in all circumstances. Reports of less complex investigations, for example, may not include safety action or appendixes.


Terminology used in ATSB safety investigation reports

Occurrence: accident or incident.

Safety factor: an event or condition that increases safety risk. In other words, it is something that, if it occurred in the future, would increase the likelihood of an occurrence, and/or the severity of the adverse consequences associated with an occurrence. Safety factors include the occurrence events (e.g. engine failure, signal passed at danger, grounding), individual actions (e.g. errors and violations), local conditions, current risk controls and organisational influences.

Contributing factor: a safety factor that, had it not occurred or existed at the time of an occurrence, then either:
a) the occurrence would probably not have occurred; or
b) the adverse consequences associated with the occurrence would probably not have occurred or have been as serious, or
c) another contributing safety factor would probably not have occurred or existed.

Other factors that increase risk: a safety factor identified during an occurrence investigation which did not meet the definition of contributing safety factor but was still considered to be important to communicate in an investigation report in the interests of improved transport safety.

Other finding: any finding, other than that associated with safety factors, considered important to include in an investigation report. Such findings may resolve ambiguity or controversy, describe possible scenarios or safety factors when firm safety factor findings were not able to be made, or note events or conditions which 'saved the day' or played an important role in reducing the risk associated with an occurrence.

Safety issue: a safety factor that:
a) can reasonably be regarded as having the potential to adversely affect the safety of future operations, and
b) is a characteristic of an organisation or a system, rather than a characteristic of a specific individual, or characteristic of an operational environment at a specific point in time.

Safety action: the steps taken or proposed to be taken by a person, organisation or agency in response to a safety issue.


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